城市人口

chéng shì rén kǒu zhōng duō shù de cháng jiàn jí bìng tā men dōu méi yǒu jiē chù dào

城市人口中，多数的常见疾病，他们都没有接触到。

They had not been exposed to most diseases common to city populations.

chéng shì rén kǒu guī mó

城市人口规模

city population scales